The present invention relates to a stator structure of an electric motor and a method for making the stator at a low production cost.
A known method for insulating a stator coil involves the use of an insulator having the width of the conductor of rectangular cross-section to be interposed between adjacent turns of the conductor. Subsequently the coil is entirely wrapped around by a cotton tape. The cotton tape is then impregnated with a thermosetting resin such as pitch varnish.
However, the taping and impregnating processes involve a substantial amount of labor, resulting in a high production cost. Since it is impossible to automate the taping process, the latter constitutes a barrier to the modernization of the whole process. Furthermore, it is difficult to ensure that the coil assembly have an appropriate dimension so that it is held tightly between 12e yoke and pole pieces. This might lead to the loosening of the coil assembly due to vibrations and a short-circuit failure would result. A further disadvantage is that the impregnating agent tends to cause a skin rash.